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<p><strong><code>trim() </code></strong>方法会从一个字符串的两端删除空白字符。在这个上下文中的空白字符是所有的空白字符 (space, tab, no-break space 等) 以及所有行终止符字符（如 LF，CR）。</p>
<h2 id="语法">语法</h2>
<pre><code class="language-javascript"><code><em>str</em>.trim()</code></code></pre>
<h2 id="Description" name="Description">描述</h2>
<p><code>trim() 方法</code>并不影响原字符串本身，它返回的是一个新的字符串。</p>
<h2 id="Examples" name="Examples">例子</h2>
<h3 id="Example:_Using_toLowerCase" name="Example:_Using_toLowerCase">使用 <code>trim()</code></h3>
<p>下面的例子中将显示小写的字符串 'foo':</p>
<pre><code  class="language-javascript">var orig = '   foo  ';
console.log(orig.trim()); // 'foo'

// 另一个.trim()例子，只从一边删除

var orig = 'foo    ';
console.log(orig.trim()); // 'foo'
</code></pre>
<h2 id="兼容旧环境">兼容旧环境</h2>
<p><code>如果 trim()</code> 不存在，可以在所有代码前执行下面代码</p>
<pre><code  class="language-javascript">if (!String.prototype.trim) {
  String.prototype.trim = function () {
    return this.replace(/^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g, '');
  };
}
</code></pre>
<h2 id="规范">规范</h2>
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<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
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<td><a class="external" href="https://www.ecma-international.org/ecma-262/5.1/#sec-15.5.4.20" hreflang="en" lang="en" rel="noopener">ECMAScript 5.1 (ECMA-262)<br/><small lang="zh-CN">String.prototype.trim</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td>Initial definition. Implemented in JavaScript 1.8.1.</td>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-string.prototype.trim" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">String.prototype.trim</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
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<td><a class="external" href="https://tc39.github.io/ecma262/#sec-string.prototype.trim" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">String.prototype.trim</small></a></td>
<td><span class="spec-Draft">Draft</span></td>
<td> </td>
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<h2 id="Browser_compatibility" name="Browser_compatibility">浏览器兼容性</h2>
<div><div class="blockIndicator warning"><strong><a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">We're converting our compatibility data into a machine-readable JSON format</a></strong>.
            This compatibility table still uses the old format,
            because we haven't yet converted the data it contains.
            <strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
<div class="htab">
<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
<ul>
<li class="selected"><a>Desktop</a></li>
<li><a>Mobile</a></li>
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<th>Feature</th>
<th>Firefox (Gecko)</th>
<th>Chrome</th>
<th>Internet Explorer</th>
<th>Opera</th>
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<td>Basic support</td>
<td><a href="/en-US/Firefox/Releases/3.5" title="Released on 2009-06-30.">3.5</a> (1.9.1)</td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td>9</td>
<td>10.5</td>
<td>5</td>
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<th>Feature</th>
<th>Firefox Mobile (Gecko)</th>
<th>Android</th>
<th>IE Mobile</th>
<th>Opera Mobile</th>
<th>Safari Mobile</th>
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<tr>
<td>Basic support</td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
</tr>
</tbody>
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</div>
<h2 id="See_also" name="See_also">相关链接</h2>
<ul>
<li><a href="Reference/Global_Objects/String/trimLeft" title="一个新字符串，表示从其开头（左端）剥离空格的调用字符串。"><code>String.prototype.trimLeft()</code></a> <span class="icon-only-inline" title="This API has not been standardized."><i class="icon-warning-sign"> </i></span></li>
<li><a href="Reference/Global_Objects/String/trimRight" title="trimRight() 方法从一个字符串的右端移除空白字符。"><code>String.prototype.trimRight()</code></a> <span class="icon-only-inline" title="This API has not been standardized."><i class="icon-warning-sign"> </i></span></li>
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